I. Field of the Invention
The present invention relates to magnetic devices.
II. Description of Related Art
Magnetic devices are used in numerous industrial applications. For example, one use of a magnetic device is known as a magnetic fanner.
In a magnetic fanner, magnets are contained within the housing having a non-metallic front wall. Typically, a pair of magnet assemblies, each having a north and south pole, are contained within the housing so that the north pole of the first magnet assembly faces the housing front wall while the south pole of the second magnet assembly faces the housing front. The magnets are spaced apart from each other.
Consequently, when a stacked pile of ferrous material is positioned next to the front wall of the housing, the magnet assemblies induce magnetic flux in the sheets of the ferrous material which causes the ferrous material to repel from each other and fan apart. This, in turn, facilitates the manipulation of single sheets of the ferrous material, especially by a robot.
In order to switch the magnetic flux in these previously known devices, an actuator was typically employed to move the magnet assemblies between a forward position, in which one pole of both magnet assemblies were positioned closely adjacent the front wall of the housing, and a retracted position in which the poles of the magnets in the magnet assembly are retracted from the front wall of the housing. In a retracted position, the magnetic flux induced through the housing front wall is reduced.
These previously known magnetic devices, however, have not proven wholly satisfactory in operation. First, even when the magnet assemblies are in their retracted position, a significant amount of flux still passes through the housing front wall. As such, the magnet assemblies still magnetically couple with ferrous materials outside the housing, even when such coupling is not desired.
A still further disadvantage of these previously known magnetic devices is that such devices lack a failsafe operation. As such, such magnetic devices may unexpectedly and undesirably shift to their operative position in which the magnets in the magnetic assemblies move to their operative position in which the magnets are positioned closely adjacent the housing front wall. This, in turn, can cause injury to personnel handling ferrous materials near the magnetic device.